Facsimile apparatus



Patented Apr. 22, 1941 UNITED sTATEsf'PATENT osi-fics FACSIMILEAPrAnA'rUs .mm v. n nomi. Foren m11, N. Y., and Home G. Miller,Belleville, N. J., assignors to Radio Inventions, Inc., New York, N Y.,a corporation of New York Application December 21, 1938, Serial No.246,972 Y Claims. (Cl.

The present invention relates to phasing of synchronized moving bodiesand in particular to framing of facsimile systems and the like.

One object of the present invention is to provide a phasing or framingmethod and apparatus vuseful in motor driven systems such asthose em--be evident from the detailed description of the various figures of thedrawing.

There are many systems involving a local oontrolling station and aremote controlled station. In general a facsimile receiving system, forinstance, must reproduce signals bearing information in a very preciserelation to the transmitter. In order to describe the present invention,it is `proposed to define this relation asbeing made up of a rate ofoperation called synchronization and a phase of operation calledframing. The rate o! operation for instance in a facsimile systememploying a long sheet of transmitted and received material willdetermine hcw received characters are related when compared to thetransmitter character relations. The phase of operation will determinehow -the characters fall withrespect to the sheet. Whilel there are anumber of ways in which the rates of operation of a facsimiletransmitter and receiver may be equalized,

one of the simplest is to operate motors driving' the transmitter andreceiver scanners from a common power source. In a system sosynchronlzed, however, the phase or framing of the receiver will dependupon the instant of turning it on and the time it takes for it to reachsynchronlsm. The present invention concerns a novel method and apparatusfor phasing or framing a ,systemas described above which is synchronizedas to the rate of operation by any one of a number ci means.

, Essentially, the invention comprises transmitting facsimile or othersignals to be recorded during a marking interval and transmitting aframseparated out and are applied to a phasing mechanism. The phasingmechanism is rendered operable during the marking interval of the relceiving recorder and is operated if framing signais are present duringthe operable or marking interval. The phasing mechanism in operation mayintroduce an impedance in series with the power supply of the receivingrecorder motor allowing it to slow down. In such a case theA amount bywhich the motor slows down depends on the duration of the framing signalin the marking interval or the amount 'of slowing may be made up ofequal increments by operating the motor circuit switch in such a mannerthat each' time it is opened it stays vopen a predetermined llength oftime. The process described above the invention.

Fig. 2 shows a schematic diagram of portions of a facsimile receiverembodying one form of the invention.

The transmitter as shown in Fig. 1 comprises marking signal generating'means of conventional ing signal during a non-marking interval. At

the receiver the marking signals are applied toa design which mayconsist in a source of sub-carrior-signal I coupled to a pick-upphoto-electric cell l and a balance network I-l by means of thetransformer 2-3-4. Photo-electric cell i is contained in the pick-upscanner It. The sub-carrier voltage modulated by thephoto-electric cellis applied acrossigrid resistor 8 to an amplifier tube l having a gridIl, plate Il, and cathode i2. Cathode I2 may receive bias from cathoderesistor I3 by-passed by condenser i4, and plate il may be loaded byresistor I5 and energized from any convenient source of plate voltage+B. The amplified modulated sub-carrier signal output from tube lappearing across plate load resistor Il is fed to a resistor I4 thrublocking condenser II. The voltage across resistor 2l is placed on grid2O of -ampliner tube 28 which also has cathode 3l and plate I3. Cathode3l receives bias from resistor Il by-passed by condenser I2 and plate Ilfeeds further ampliners,` carrier modulators. etc. u comprising thetransmitter feeding antenna A. In the case of a wireline 34 may be anycoupling system suitable to the particular type of line.

'I'his invention as far as the transmitter. is conmarking member and theframing signals are cerned comprises means for introducing aphasimpulses.

tion i8 of cam I8-i9- which closes contact 22 thereby feeding modiulatedsub-carrier signals from resistor 24 to resistor 26 and from there tothe transmitter 34, causing marking signals to be emitted. During theremainder of the scanning cycle or non-marking interval the largerradius l portion I8 of cam I8-I9 opens switch contact 22 removingmarking signals from the transmitter, and closes contact-23, placingphasing sig..

nais from source 21 on the transmitter. The frey quency oi' source 21 ismade suiciently different from the frequency of sub-carrier li thatthetwo signals and the modulations oicarrier I may be differentiated ona frequency basis in the receiver.

,Thus, the transmitted signal is made up of marking signals and framingsignals, although there may also be short intervals of `zero signalbetween each switch-over while switch --2I--22-23 is in a neutralposition. This interval may be con- -trolled by varying the slope of thecam surface between the smaller radius I8 and the larger radius i8, andby varying the space between contacts 22 and 23.

The receiver as shown in Fig. 2 comprises a conventional facsimilereceiver 35 attached to antenna A. After amplication and detection thereceived signals consist of marking signal ,modulations of the rstsub-carrier, intervals of no signal and the phasing signal sub-carrierThis composite signal is applied to a separator circuit comprising tunedtrap circuits 38--31 and SMQ. Trap 3 8-31 is tuned to the marking signalsub-carrier and the marking signals thereby established across it areapplied to the receiver scanner I2. at points III-4i where mally heldopen to close contact Il by spring 15. Contact $8 is placed acrossanimpedance comprising condenser 1I shunted by resistor 12 in serieswith the scanner motor 60 and its power supply leads 13-14. Cndenser 1|and resistor 12 are so chosen that when contact 68 is opened as`described above, motor 60 slows down. 'I'he rate at which it slows downmay be controlled over a range by the choice of condenser 1I andresistor 12. Thus, if phasing signals are received at the receiverduring the marking interval, the driving motor Sil' is slowed down Motort@ may be a synchronous motor operated from the same alternating currentpower source, as the'transmitter or other synchronizing systems may beused to maintain rate synchronism as defined above. It will be seen thatwhen in frame no mark will be produced on the back stroke, since theframing signal is not passed by trap circuit td--BL As described, thereceiver motor 60 is slowed down during each cycle of scanning by anamount which depends upon the amount by which the re- Y ceiver scanneris out of phase with the transit may be lfurther amplified and rectifiedand utilized to energize or operate a recording electrode or othermechanism. Trap circuit 38-3@ is tuned to thephasingsignal sub-carrierfrequency and voltages appearing across it are applied to' grid i4 ofamplifier tube Qt also having a plate t6 and a cathode dii connected tobias resistor 38 by-passedv by condenserel. The plate t8 feeds relaycoil its and is. energized from any suitable voltage source at +B. Thus,phasing signals operate the relay associated with coil il@ comprising acore 50, armature 5l, `return spring 52, contact 5l and stop 54.Recorder 42 is run by motor BI) from shaft 6|. A counter-shaft 59 isprovided which revolvesvcam 51--58 once for each scanning cycle as wasthe case' of cam I8- IS. Cam 51-58 moves contact 55 into and out ofoperating position thru roller S6. When roller 5t ison the smallerradius 5t as shown, contact 5t cannot be closed by phasing signals. butwhen roller 5t is on` the larger radius El, contact .EE may be closed byphasing signals. Thus, if phasing signals are received during themarking stroke of the receiver, that is while roller 66 is onlargerradius 51, contact will close with arm 5I and a. circuit will becompleted from wire 53 to wire 66 thru relay coil 65. Wires S3 and $4are connected to a source of electrical energy suitable for energizingcoil to open contact il oi' relay 8548-41-82.

mitter scanner. When the twoare in phase, there will be no furtheraction of the phasing system as long as synchronism is maintaineduninterrupted.

Cams I8 and '51 have been shown cut for equal recording andnon-recording intervals for each with small, no signal intervalsprovided for between marking and framing signals. `In many cases it isdesirable for efciency of operation to mark for more than half the timeand to transmit framing signals during only a small time interval, sayfor 15 percent of each scanning cycle. This may easily be accomplishedby making the larger diameter of cam' it 54 degrees to transmit framingsignals for i5 mrcent of each cam revolution and the smaller diameterportion Fit of the cam at the receiver likewise 54 degrees so that thephasing system is operable for 306 degrees, or the marking portion ofeach scanning cycle. l im 1 A variation of the mode of operationdescribed may be accomplished by delaying the closing of contact t onceit is opened by means of a slow return plunger it operating in a dashpott9. If imance iis made to have only a small eiiect on the speed of motorit@ and the slow return mechanism ci contact @t is made to have a longperiod compared to half a line scanning Armature 61 is nor- 75 cycle,the phasing will be accomplished by equalincrernents no matter how muchor little the phasing is out, until perfect phasing is accomplishefd, orphasing increments may depend upon the amount by which phasing signalsoverlap thev marking intervals when phasing is out by a large amount,and these increments may decrease as phasing is corrected to a limitingincrement determined by the time of operation of the dashpot or asimilar time delay device. If idle periods between the phasing andmarking signalsA are provided, as described above, the phase relationwill be corrected to be nearly perfect, `but may be out by the amount cithese idle periods. lThe idle periods may correspond tc a margin in thereceived material, so that a quieter but less accurate phasing may beaccomplished only at the expense oi margin space. With increased markingtime, the equal increments of phase correction become increasinglyimportant.

One outstanding advantage of this present framing system is that oncethe system is framed, interference cannot, aect" the framing during apart of each lcycle. During the/remainder of the lMamas cycle,onlyinteriklerencel having strong com-` for instance, amplitudeselection, may be used to separate marking and framing signals. Againframing signals may-be transmitted for all or only a part of non-markingintervals. Short impulses of framing signals may be utilized in whichcase equal-increments of framing may be utilized tofull advantage byproper choice of timeiof operation of dash pot 68-10.

, vals, andmeans for shifting the phase. of said. motor by an amountproportional to the duration In Figs. 1 and 2 the letter G representsground points or common. points'as is electrical circuitrepresentations.

' While one embodiment, with a, few modifications, has been shownvention embraces these and other modifications as will be evident to.those as set forth in the appended claims.

What is claimed is:

1;'In a facsimile system, the combination of, a facsimile receiver, afacsimile recorder, a synconventionalin chr'onized motor for'operatingsaid recorder, in-

dependent means responsive to signals comprising two distinct groups offrequencies, means for dividing receiving' periods into recording and'Anon-recording intervals, means for slowing said motor in accordance'withnone of said groups of frequencies when received during saidrecording intervals and means for equalizing the slowing of said motorregardless of the duration 0f reception of said last groups offrequencies during said recording intervals. Y

2. In afacsimile receiving system, the combination of, a recorder, asynchronized motor forl driving said recorder, means for dividing re-`ceiving periods into recording and non-recording intervals, meansforreceiving marking and phasing signals comprising two distinct groupsof frequencies, means for separating said two groups and described, the.in-

skilled in the art,

' for driving said recorder,

vals, and means for changing the phase of said motor in response to saidpresence. v 3. In a facsimile receiving system, the combination of, arecorder, a synchronized motor for driving said recorder, means fordividing re' ceiving periods into recording and non-recording intervals,means for receiving marking and phasing signals comprising two distinctgroups of frequencies, means for separating said two groups offrequencies, means for detecting the presence of phasing signalsduringsaid recording interof said phasing signals present during saidrecording interval.

4. In a facsimile receiving system, the combination of, a recorder',vsynchronized driving means for said recorder, means for dividing re-`ceiving periods into recording, non-recording and margin intervals,mea-ns for receiving frequency distinctive marking and phasing signals,and means for phasing said driving means in response to phasingsignals'received during said recording intervals whereby said markingsignals are recorded during said recording intervals plus said marginintervals.

5. In a facsimile receiving system, the combination of. a recorder, asynchronized motor means for dividing receiving periods into recordingand non-recording intervals, means for receiving marking and phasingsignals comprising two distinct groups of frequenciearmeans forseparating said two groups of frequencies, means for detecting thepresence of phasingsignals during said recording intervals, means forchanging the phase of said motor in response to said presence, and meansforv controlling the amount of phase change to be produced relative tothe durati l of said phasing signals during said recording intervals.V

JOHN V. L. HOGAN. HORACE G. MILLER..

of frequencies, means for detecting-the presence of phasing signalsduring said recording inter-

